<!DOCTYPE html>
<html>
<head>
  <title>Bootstrap 实例 图片</title>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="stylesheet" href="https://cdn.staticfile.org/twitter-bootstrap/4.1.0/css/bootstrap.min.css">
  <script src="https://cdn.staticfile.org/jquery/3.2.1/jquery.min.js"></script>
  <script src="https://cdn.staticfile.org/popper.js/1.12.5/umd/popper.min.js"></script>
  <script src="https://cdn.staticfile.org/twitter-bootstrap/4.1.0/js/bootstrap.min.js"></script>
</head>
<body>
圆角图片
<img src="1.jpg" class="rounded" alt="Cinque Terre">
<br>
椭圆图片
<img src="1.jpg" class="rounded-circle" alt="Cinque Terre">
<br>
缩略图
<img src="1.jpg" class="img-thumbnail" alt="Cinque Terre">

<br>
响应式图片
<img src="1.jpg" class="img-fluid" alt="Cinque Terre">


</body>
</html>